As technology advances, devices continue to shrink in size and it becomes increasingly difficult to test or verify the operation of the devices. One example of this is found in storage systems based on magnetic recording technology, which is commonly used in devices such as computers and digital electrical household appliances. In operation, a magnetic write head is used to magnetize bits of data on a recording medium, commonly referred to as a hard disk, while a read sensor is used to read the bits of data from the hard disk.
It is desirable to test devices, such as read sensors and write heads, early in the manufacturing process to increase yield and reduce costs. However, as devices, such as the read sensors and write heads, continue to shrink in size it is increasingly difficult to perform accurate measurements early in the manufacturing process. For example, a write head uses a write pole that has a size that is below the resolution of conventional optical imaging techniques. Accordingly, to image the write pole, typically a scanning electron microscope (SEM) is used. However, SEM is an expensive, time consuming test that is potentially destructive. Another method of testing a writer is with Magnetic Force Microscopy (MFM), where an MFM probe scans across the surface of the write pole while the writer is excited with a current. Alternatively, a spin-stand is sometimes used to test the write head. However, a spin-stand test is also an expensive and time-consuming test.